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Pilocytic astrocytoma (py-loh-SIT-ik as-troh-sih-TOH-muh) is a slow-growing brain tumor that usually affects children and teens. The term "pilocytic" refers to the cells' long, hairlike shape as seen under a microscope. The term "astrocytoma" means the tumor starts in star-shaped brain cells called astrocytes.
Pilocytic astrocytoma is a type of brain tumor called glioma, which begins in a glial cell. Glial cells support and protect nerve cells in the brain and help them function properly. Pilocytic astrocytoma grows from a type of glial cell called an astrocyte. Astrocytes help keep the brain working smoothly. They maintain the right conditions around brain cells by managing chemicals, fluids and waste. They also support communication between neurons.
Pilocytic astrocytoma is the most common type of glioma in children. Pilocytic astrocytoma often develops in the part of the brain that controls movement and balance, called the cerebellum. These tumors also can appear in other structures including the optic nerve, brainstem, spinal cord or other parts of the brain.
Most pilocytic astrocytomas are noncancerous, also called benign. Symptoms depend on the tumor's location but may include headaches, nausea, balance problems, vision changes or behavior changes.
Pilocytic astrocytomas are classified as grade 1 tumors by the World Health Organization (WHO) scale for brain tumors. Grade 1 tumors are considered the least aggressive brain tumors. Grade 1 indicates that the tumor:
- Grows slowly.
- Is well defined and has clear borders.
- Has a low risk of spreading.
- Often responds well to just surgery without additional treatment.
Pilocytic astrocytomas were previously called juvenile pilocytic astrocytoma (JPA) because the condition is more common in children. Currently, pilocytic astrocytoma is the term used for both adults and children with the condition.
Treatment for pilocytic astrocytoma usually involves surgery to remove the tumor. If the tumor can be completely removed, no other treatment may be needed. When the tumor can't be fully removed or it grows back, other treatments such as chemotherapy, targeted therapy or radiation may be used.
The prognosis for people with pilocytic astrocytoma is usually very good, especially when the tumor is found early and can be fully removed.
Symptoms of pilocytic astrocytoma
Symptoms of pilocytic astrocytoma can vary depending on the tumor's size and where it's growing in the brain. These tumors grow slowly, so symptoms may develop over weeks or months and get worse over time. Many of the signs and symptoms of pilocytic astrocytoma are caused by increased pressure in the brain or by the tumor pressing on nearby structures.
Children with tumors near the cerebellum or brainstem may show signs earlier because those areas control balance, coordination and vital functions.
Pilocytic astrocytoma symptoms in children usually are not different from pilocytic astrocytoma symptoms in adults. The location of the tumor, rather than age, determines the type of symptoms you have.
Physical symptoms of pilocytic astrocytoma
- Headache, which is often worse in the morning and may change with position.
- Nausea and vomiting.
- Problems with balance or coordination.
- Vision changes, such as blurred or double vision.
- Weakness in the arms or legs.
Hormone-related symptoms of pilocytic astrocytoma
Pilocytic astrocytoma can cause hormone-related changes that may affect growth or puberty:
- Hormone changes. If the tumor is near the hypothalamus or pituitary gland, it may disrupt hormone signals, affecting growth or puberty.
- Delayed or early puberty. Some children may start puberty earlier or later than expected.
- Slowed growth. Pilocytic astrocytoma tumors around the hypothalamus can lead to slowed growth or failure to grow as expected.
Cognitive and mood-related symptoms of pilocytic astrocytoma
- Changes in behavior or personality.
- Difficulty with memory or thinking clearly.
- Mood swings or emotional changes, such as irritability or sadness, may occur in some people.
Other neurological symptoms of pilocytic astrocytoma
- Seizures, though these are less common with pilocytic astrocytomas than with other brain tumors.
- Difficulty with speech or understanding language.
- New difficulties with movement or coordination, such as clumsiness or stumbling.
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The exact cause of pilocytic astrocytomas isn't known. Most of these tumors happen without a known trigger. However, scientists have found certain factors in genes and the environment that may play a role in the growth of pilocytic astrocytoma tumors.
Many pilocytic astrocytomas are linked to changes in the mitogen-activated protein kinase (MAPK) pathway. This pathway is a system that helps cells communicate and controls how cells grow and divide. These changes can trigger growth signals in brain cells and may lead to tumor growth.
At this time, there's no proven link between pilocytic astrocytomas and environmental factors such as cellphone use, diet or chemical exposure.
Risk factors for pilocytic astrocytoma
While experts don't know exactly what causes pilocytic astrocytoma, researchers have found some risk factors that may raise a person's chances of developing this kind of tumor:
Inherited genetic conditions
- Neurofibromatosis type 1 (NF1) is the most well-known inherited risk factor. People with NF1 are more likely to develop pilocytic astrocytoma, especially in areas near the eyes and the hypothalamus, deep in the center of the brain.
- Other rare syndromes, such as Li-Fraumeni syndrome and tuberous sclerosis, also may increase the risk of developing pilocytic astrocytoma.
Age
- Pilocytic astrocytoma is most common in children and teens.
- Although rare, adults can develop pilocytic astrocytoma. It may be more aggressive in older people.
Other possible associations
- Some studies have noted a slightly higher rate of brain tumors, including pilocytic astrocytomas, among farming and petroleum workers, but this link is not well understood.
- Radiation exposure to the head in childhood, such as during cancer treatment, may raise the risk of some brain tumors.